Corpulent sex slaves, tuba-playing Nazi obsessives, reborn doll fantasists -- just a regular stroll through the neighborhood, then, for patented guru of the grotesque Ulrich Seidl, who makes an intriguing return to documentary filmmaking with "In the Basement." Grabby and grubby in equal measure, this meticulously composed trawl through the contents of several middle-class Austrians' cellars (a space, according to Seidl, that his countrymen traditionally give over to their most personal hobbies) yields more than a few startling discoveries. It's not hard to tell, though, that a mixture of fact and fabrication is at work here. The career-high success of Seidl's recent "Paradise" trilogy should boost the distribution prospects of

It's impossible to read even the barest logline for "In the Basement" without thinking immediately of Josef Fritzl and Wolfgang Priklopil, whose unrelated but comparable crimes -- the horrific confinement, in their respective basements, of young female victims for years on end -- prompted even Austria's political leaders to fear for the country's international image. Recent Austrian cinema hasn't done much to soothe the situation, with numerous works (Markus Schleinzer's "Michael" most directly of all) dwelling on the social aftermath of the cases, as well as their nation's much-discussed culture of secrecy. Seidl's latest isn't his first film to fit that bracket, though press notes claim he conceived it years before the Priklopil scandal broke in 2006.

Indeed, the helmer has been upturning the paving stones of Austrian suburbia to unsavory effect throughout his career. The affectionate crowd applause that greeted "In the Basement" at its Venice premiere suggests that his work, through no failing of his own but consistency, may have lost some of its incendiary capacity. What it has regained, however, following the unexpected warmth and qualified optimism of last year's "Paradise: Hope," is some of its chill. From first frame to last, this is an arm's-length exercise in observation, even in scenes of discomfiting intimacy. At least, it poses as one: As in his other documentaries, it's left to the viewer to imagine just how much Seidl has staged or manipulated these human tableaux, though the degree to which they reflect his signature aesthetic and tonal quirks leaves little doubt as to his complicity. (Does everyone in Austria line up their radiators quite so precisely with their narrow, uniformly net-curtained basement windows? Perhaps.)

Things start innocently enough, with a middle-aged, drably-sweatered man (amusingly named Fritz Lang, though the film's participants are identified only in the closing credits) using the acoustics of a cavernous basement to flex his impressive tenor high "C" on a range of operatic standards. That he's doing so before a row of target practice sheets, admittedly, seems a little odd; it emerges that he runs a local shooting gallery, where graying local menfolk come to let off steam and exchange politically incorrect bugbears. Not half as politically incorrect, however, as Josef, a married, mild-mannered fellow whose basement is a densely art-directed gallery of Nazi memorabilia, regarded with little curiosity or concern by his fellow brass-band players who routinely use the space for rehearsals.

Others use their underground space for sexual release: A pneumatic young woman who has quit her job as a supermarket teller to become a prostitute, a former victim of domestic abuse who has found strength in controlled sadomasochism, and a married couple whose indoor relationship is of an extreme mistress-slave nature. The latter subjects gamely provide the film's most queasily NC-17 material, as the heavy-set, hairy-backed Gerald attends to his dominant wife's every whim, licking her genitals clean after urination while his own are subjected to wince-worthy punishment in the couple's crimson sex dungeon. No sections of the film are more haunting, however, than those spent with kindly-looking Alfreda, whose tiny basement storage unit is stacked with creepily lifelike reborn dolls, each one stored in a separate, tissue-lined box, to be removed, cuddled and comforted at will.

Seidl's approach is not to press these ostensibly ordinary folk for expression or explanation; some offer less than others, with the men in particular giving mostly prosaic descriptions of their basements' contents and histories. We are never told, for example, whether Josef is actually a Nazi sympathizer or whether his disturbing collection is of purely historical interest. (His default reference to the modern-day police as "the Gestapo," however, raises certain inklings.) That affectless approach will frustrate viewers craving more neatly articulated insights into Austria's supposed social singularities; others, meanwhile, will accuse Seidl of not being objective enough, as his stylistic affectations and interferences with reality may create aberrance or uncanniness where there is none. (He has admitted, for example, to constructing a narrative for Alfreda, who is not in fact a doll collector.) Accept his debatable methods, however, and certain profundities emerge: The way several of his female subjects take advantage of below-stairs privacy to reverse conventional gender roles and assert themselves sexually is particularly powerful.

Working for the first time with the brilliant cinematographer Martin Gschlacht -- best known for his similarly geometric work with fellow Austrian Jessica Hausner -- Seidl has found an ideal creative enabler for his vision. The carefully calibrated gloom of Gschlacht's lighting schemes (all the better to accentuate the frequently bilious colors of the decor) and the sharpness of his seemingly tweezer-set framing often suggests more about these "characters" than they are willing to say about themselves. Christopher Brunner's editing is equally crisp and incisive, and while no production designer is credited, Seidl has apparently chosen subjects who share his eccentric taste in interiors. Even a wall cluttered with African mementoes and macabre taxidermy trophies manages, through Seidl's gaze, to look strangely austere.